A tennis shaft or frame is generally produced by winding one or more prepregs around a core material and then heating in a mold. The prepregs are composed of thermosetting resin and reinforcing fibers embedded therein. As the reinforcing fibers, carbon fibers and glass fibers have been employed for years. In order to improve strength, flexibility, impact resistance, feeling when hitting balls (i.e. vibration absorption etc.) and weight saving, aromatic amide fibers and aromatic polyester fibers are also proposed together with carbon and glass fibers in Japanese Kokai Publications 69870/1982, 142572/1987 and 141678/1989.
The aromatic amide and polyester fibers, however, are too tough and associated with problems in producibility in the case of being embedded as a sole layer. For example, in a drilling process for creating holes for passing gut through the frame of the racket, to drill such holes due to the toughness of the aromatic amide or polyester fibers embedded in the tennis racket frame. Also, in a buffing process for smoothening the surface, fuzzing often occurs. Furthermore, the inter laminated shear strength would be insufficient because of different physical properties among adjacent laminated layers.